package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;


@Slf4j
@Component
public class CacheClient {
    private StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit)
    {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    //尝试获取锁
    private boolean tryLock(String key)
    {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unLock(String key)
    {
        stringRedisTemplate.delete(key);
    }
    public void saveShop2Redis(String key, Object value, Long time, TimeUnit unit)
    {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit)
    {
        String key = keyPrefix + id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否命中
        if(StrUtil.isNotBlank(json))
        {
            //存在直接返回
            return JSONUtil.toBean(json, type);
        }
        if(json != null)
        {
            return null;
        }

        //不存在根据id查询数据库
        R r = dbFallback.apply(id);

        //判断是否为空
        if(r == null)
        {
            //若为空则将null写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //存在则将值写入redis
        this.set(key, r, time, unit);
        return r;
    }


    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    //逻辑过期解决缓存击穿问题
    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit)
    {
        String shopKey = keyPrefix + id;
        //1.从redis查询商品缓存
        String json = stringRedisTemplate.opsForValue().get(shopKey);
        if(StrUtil.isBlank(json))
        {
            //若存在直接返回
            return null;
        }
        //若redis缓存命中
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject shopData = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(shopData, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if(expireTime.isAfter(LocalDateTime.now()))
        {
            //未过期直接返回店铺信息
            return r;
        }
        //已过期需要进行缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        if(isLock)
        {
            if(expireTime.isAfter(LocalDateTime.now()))
            {
                //未过期直接返回店铺信息
                return r;
            }
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    //重建缓存
                    //查询数据库
                    R apply = dbFallback.apply(id);
                    //写入redis
                    this.queryWithLogicalExpire(keyPrefix, id, type, dbFallback, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //2.若缓存中不存在则需要查询数据库
        return r;
    }



}
